In giant snow piles, on the bottom of your car and in almost any parking lot is a sign of the season — sodium chloride, or road salt, left behind.

“We’re seeing this chloride from road salt building up in surface water of our lakes and streams,” says Andy Erickson, research manager with the St. Anthony Falls lab at the University of Minnesota. “We’re seeing it build up in our groundwater. Some of our drinking water wells are starting to taste salty.”

The Minnesota Pollution Control Agency (MPCA) says statewide about 404,000 tons of road salt are used every year.

The idea is to keep roads safe, but there’s also an environmental impact.

“Definitely there’s going to be some salt in those snowbanks and also, just a lot of snow accumulates on the ground, and into those ditches, and our stormwater ponds,” declares Brooke Asleson, chloride reduction program coordinator with the MPCA. “The chloride component of salt is actually toxic to our freshwater fish and insects and plants that live in our lakes and our streams and wetlands.”

So now, researchers at the St. Anthony Falls Laboratory in Minneapolis and the Natural Resources Research Institute (NRRI) in Duluth are looking into road salt alternatives.

“Sodium chloride, salt, doesn’t go away,” explains Chan Lan Chun, an institute researcher. “So, once it gets into the water, it kind of stays there.”

The NRRI did two companion studies.

One looked at locally sourced materials to improve traction on the roads, including taconite waste rock and ground bark, a wood byproduct.

The other involved research into potassium acetate, a chemical made with vinegar used to de-ice airplane wings.

“It is effective as a de-icer, then potentially it can be degradable, so it goes away in the water,” Chun explains. “When we use rock salt, it kind of corrodes bridges or concrete, but the potassium acetate isn’t corrosive in nature, so that’s another benefit.”

“It reduces the melting temperature so that even though it’s cold, it can still melt that cold and ice,” Erickson adds. “Because it’s organic, it will naturally bio-degrade and break down in the environment, so it has much different and less impact than salt will.”

There is a wrinkle, however.

It turns out potassium acetate is expensive — six to eight dollars a gallon.

Experts say the salt travels from our roadways into storm drains, ending up in lakes and other waterways.

The problem is that salt is cheap, about 50 cents a gallon, and finding alternatives isn’t easy.

MnDOT engineers say a mix of salt and brine may be a winning formula.

In recent years, the department has used 15 million gallons of the stuff annually.

“One test, we reduced our total salt amount by 30%,” says Jed Falgren, the MnDOT state maintenance engineer. “Got the road cleared faster by about 30%. By using less materials, we reduced our environmental impact and reduced our costs.”

Some communities are trying other techniques.

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Shoreview, for example, is using permeable pavement, which allows snow and ice to melt downward.

That means less standing water and little to no salt used.

“It goes from the pavement directly into the ground, so you don’t have that issue of wet roads and running water that can tend to refreeze,” says Ted Wesolowski, the city’s Public Works director. “Typically, in the areas where we have permeable pavement, we don’t use salt or products like that to melt down the water.”

By pre-treating with brine, Wesolowski says the city’s salt use has declined 30%.

Asleson says the MPCA has connected with government agencies and private companies with an initiative called ‘smart salting’ training.

“One of the first steps is making sure the equipment is calibrated properly,” she explains. “There is this misperception that more salt will speed the process up or provide safer conditions, and that’s just not true.”

‘Hold the salt’ is the new mantra as communities look for ways to keep roads and the environment safe.

Erickson says researchers will keep looking for answers.

“Ground bark and sand and grit and even taconite, those are all things we use to increase traction on our roads,” he explains. “My biggest hope is looking at other chemicals, maybe in combination with acetate that could work well and have less environmental impact. And we are working that way.”